Dry kiln



mes. 13 1932. I v MWQBE 7 1,891,660.

DRY KILN Filed July 7, 1927 4 She ets-Sheet l dvi a gwuento'a Dec. 33,1932.

J. F. CQBB DRY KILN 4 fsneets sneet 5 Fild July 7, 1927 attozmqf J. F.COBB Dec. 13, 1932,

DRY KILN Filed July 7, 1927 4 Sheets-finest 4 I attorney 3;

I s 1 v gwue'nto'qp Patented at. s, 1932 JAMES Fonans'r cone, orroarnann, oaneon DRY KILN Application filed July 7, 1927. Serial 1%.204,022.

My invention relates main] to the art of kiln drying of lumber or ot ersubstances,

buthas for one. of its principal objects the roduction of a novelportion of a drying iln, hereinafter denominated a multiplex fan unit.

Another object of my invention is to produce im roved means forefi'ectin the circulation of the drying atmosphere 0 a dry kiln, whereinthe preferred means employed for efi'ecting such circulation is theaforesaid multiplex fan unit whose use is attended by definite advantageover other means of producing circulation, as will appear to one skilledin the art from the specification which follows.

Another object of my invention is to produce an effective forced aircirculation within extended duct compartments by means of a singlereversible fan system.

Still another object of my invention is to produce a unified circulationtransversely through a series of loads of lumber in a kiln, from oneplenum chamber in one portion of the kiln to a suction chamber inanother portion of the kiln.

What constitutes my present invention will be hereinafter described indetail and succinctly defined in the ap ended claims.

In the accompanying rawings:

Figure I is a longitudinal horizontal section of one form of embodimentof my invention, complete, com rising illustration in plan of mymultiplex an unit which is the means preferred, by reason of itsincrease of efiiciency, for producing forced circulation of theatmosphere of the kiln chamber, shown in Fig ure II.

Figure II is avertical transverse sectional view taken on the line IIIIof Figure I.

Figure III is a detached side elevation of one of my multiplex fan unitsshown on smaller scale in Figure I.

Figure IV is a view similar to Figure I, showing two complementarycoacting fans of the kind shown in Figure III.

Figure V is a vertical transverse sectional view taken on the line VV ofFigure IV.

Figure VI is a view, similar to Figure IV, but showing a modification ofmy invention in respect to provision. of a plurality of separatecombined heating-and-circulating units instead of the single unit shownin other figures.

Figure VII is a view similar to Figure I, for example, but showing avariation consisting of a single fan located on the outside of but inoperative communication with the interior of the kiln.

Figure VIII is an end elevation of the subject matter of the lastpreceding figure, partly in section.

Figure IX is a diagrammatic longitudinal View showing a trunk having atapered slit for a port, instead of ports comprising a series ofseparate openings of graduated size disposed in endwise succession inthe trunk.

Figure X is a like view showing a convertible duct comprising an oblongtrunk or casing, say of rectangular shape in cross section, a snuglyfitting cover-plate movable above the case upon a medial pivot over aseries of transversely oblong openings, with the efiiect of defining aseries of ports which, by pivotal movement of said plate, may be made totaper in size, respectively, towards one end of the trunk or towards theother end of it, at will.

Figure XI is a View similar to Figure II,

showing a kiln enlarged to accommodate on two tracks a series oflaterally disposed loads of lumber.

Referring to the numerals on the drawin 1 indicates, in Figures I, III,and IV, or example, what I call a multiplex fan unit that is operativelyencased by preference only in any suitable housing, the elementswhereof, in various instances, are hereinafter indicated.

The fan mechanism, in respect to my invention, in all forms ofembodiment thereof, is required to make air delivery to its properelongated duct or trunk with force suflicient tocreate effective staticpressure within said duct from end to end thereof. For this purpose Ihave found my multiplex fan unit 1 especially well adapted forextensively elongated ducts or trunks.

By the term multiplex fan unit, I desi ate a fan unit consisting of aplurality 0 any 100 iii preferred number of o eratively groupedindividual fan blades 2 fixed, as shown, for example, in Figure III,upon a common shaft 3 in cooperative pro inquity and relativedispositionone to anot er in the order of their sequence on the shaft, and allmaking a common air delivery lengthwise of the shaft in one direction orthe other accordin to the direction of rotation of the shaft. he fanscomprising blades 2 are preferably of the reversible disc type, wherebythe fan unit may be rotated effectivel in either direction.

The fan blades may be arranged in any preferred number relativedisposition on the shaft 3, T e may be, for example,

" short in a succession of circuseries, as lustrcted, or in other caative disposition relatively one to The posed in circular series adesare iliustrated in the drawings as a spaced equidistantly from eachotheralong len th oi the shaft 3, but it should be observed that my inventionin this regard, contemplates variation between the individual fan bladesas well as between the circular series of blades it employed.

this connection, it is important to note that the first series of bladeswhen in rotation acts upon the incomin air so as to impart to it amomentum whic is in turn communicated to the next series, and by itaugmented, and so on throughout the sequence of series along the shaft3. Consequently, it is deemed advantageous in some instances, determinedpartly by working conditions, to

radually increase the distances betwen the i an blades or the successiveseries of blades in order to utilize the force of momentum oi the airgenerated in passing through the entire range of series.

I have discovered that the multi lex {an unit, constructed substantiallyas escribed above, has the efiect, in-operation, of greatly increasingthe force and efi'ective reac of its air deliver in direction endwisc ofits shaft over what as been heretofore possible by the use of disc fans,thereby rendering it peculiarly available, under some conditions, foraccomplishing the end proposed in respect to my dry kiln hereinspecified. Under some conditions, however, other forms of fans forinducing circulation may be emplo ed to advantage, as hereinafterindicate by way of exam le.

My kiln comprises a kiln-chamber 5 made of any suitable material, shape,size, and dimensions, such as are well known in the art or such as maybe adapted for the purpose as oocasion may demand. The chamber 5 has abottom floor 6, and a horizontal wall or walls 7, above which, withinthe kiln-chamber, kiln loads 9 of drymg stock that are permeable to aircirculation, are carried, usually upon railsupported trucks, which beingof common use in dry kilns are deemed to require no further illustrationherein than that which is suggestively presented in Figures II and V,for example.

In Figure XI, a plurality of loads 9 in lateral communication one withanother within one kiln is shown.

In Figures 1, II, IV, V, and VII, I illustrate a plurality of say twotrunks, 10 and 11, in paired relationshi which are separated irom eachother y an imperforate vertical wall 12. which being somewhat shorterthan the trunks, serves, to the extent of its length, as a closurebetween the iioor 6 and horizontal wali Y. One wall 7 -for the :fullcomplement of trunks may be employed, or one for each 'iilh is be used.

plurality of? more th n trunks be employed, 5'-

s will be, oi cor tional pairs of tru fine or each pair of tr in use ora chamber wherein static pressure is, by suitabie means, for example the1, built up, and the other suction chamber. Air supis, in such case,communicated under pressure to the interior of the trunk 10 below itswall fr, which is provided with ports 15, referably oi the louvre typeif fans for e ecting circulation be employed, and constituting, in theinstance assumed, eduction ports for afiording means of communicationbetween the trunks 10 and 11 as aforesaid,

By reason of and in respect b0 the reversibiiity of the direction ofcirculation within the kiln of the circulatory medium, otherwise hereinfor brevity denominated air, which is contemplated in some forms ofembodiment of my invention, it should be understood that the ports 15may be, in such case, alternately converted at will into induction oreduction ports. Wherefore, I employ the common term ports as one ofsufiicient identification of them.

The trunk 11, being, for the instant, assumed the suction chamber, isalso provided, like the trunk 10, with ports 15. In 0 eration,circulation within the interior 0 the kiln-chamber 5 passes incontinuous flow (however regulated) above the wall 7 from the plenumchamber, say 10, to the suction chamber, say 11, through the ports 15 inthe wall 7 of the respective chambers, and from the suction chamberaround the end of the partition wall 12 back to the plenum cham- Theports for each trunk may be arranged as a series of separate aperturesof graduated capacities, respectively, or by equivalent means forefiecting a graduated force of delivery, such, for example, as a taperedseries of slits 15, which are in familiar use in the art, of such otherports as may be devised and ads ted for the pur ose.

In di erent figures oft e drawings, I illussup lying the trunks 10-11,for example,

wlt am For instance, in the preferred form of embodiment of my inventionillustrated in Figure I, the multiplex fan unit 1 is the one preferablyused. In Figure IV, two mult1plex fan units 1,7 and 18 mounted onseparate shafts 19 and 20, respectively, are shown mounted within thetrunks 10 and 11, res ectively. The fan units are contrived to ma e airdelivery in opposite directions. Said shafts may be to that end, andpreferably are, operatively united by a common driving belt 21 mountedon pulleys 22 and 23, fixed tothe said shafts, res ectively, so as torotate them in the same fans 17 and 18 being right and left hand fans,respectively. make air delivery in opposite directions. They areoperably connected, as by a belt 24and a pulley 25 fixed on the shaft19, for example, to the shaft 26 of an electric or other motor.

In Figure VI, the trunks are, by transverse partitions 28, divided intoa pluralityof sets, say three, of separate plenum chambers 29, 30, and31, each plenum chamber being provided with a preferably singlepropulsion fan respectively designated by reference numerals 32, 33, and34, and a corresponding plurality of suction chambers, 35, 36, and 37,each provided with a suction fan numbered 38, 39, and

40, respectively. Heating units 41, in sufficient number to meet heatingrequirement,

are provided for each of the plenum and suction chambers, which areseparated one from another by partitions 42. In other words, theconstruction shown in Figure Vii is, in effect, simply a transversedivision of the trunks 10 and 11 into series of three independent trunksdisposed in end to end assemblage, and separated by the respectivepartitions 28. The sets of fans 32, 33, and 34, are fixed to a commonshaft 43, and the fans 35, 36, and 37, are fixed to a common shaft 44.

The shafts 43 and 44- may be driven by means corresponding to that shownin Figure IV, for example, as means already described for driving theshafts .19and 20.

In Figure Vll an external multiblade fan -16 of usual or other preferredconstruction, is diagrammatically illustrated instead of the internaldisc fans shown in the other figures, and is intended to indicate that anon-reversible fan disposed outside the kiln-chamber as Well as areversible fan of the internal fan type is contemplated as available foruse in my present invention. 7

In each figure of the drawings a suilicient complement of heating units,which may be of any suitable tv e preferred, is provided for each trunk.or example, in Figures I and IV, heating units 47 consisting oflongitudinally disposed heating coils, are shown. In F i ures VI andVII, transversely disposed heaters 41 aforesaid are shown; but itirection, but the spect to my present invention,

should be observed that either of said forms,

of heaters may be used interchangeably, or

other heating units of any known or suitable form may be, at will,employed in any form of embodiment of myinvention.

The circulation of air produced up one. side of the load, thencetransversely between the layers of permeably stacked stock constitutingsaid load and thence down the op 0- site side of the load, gives agreater velocity of air movement than if the currents were divided, andthus that method of circulation increases the ca )acity'of the kilnwithout increase of expenditure of power for producing circulation.

It should be also understood that in rethe employment of any usual or another suitable and preferred means for ad: commonly em loyed incontemplated by me, such, or example as an means preferred, forefiecting ventilation, heat control humidificaton of the kiln, and aircurrent directing bellies. I show, for instance, humidifying andauxiliary circulator sprays 45, damper-controlled vents 48, and freshair intakes 49. Such instrumentalities as are above named, or the likeincidentals usual in kiln drying operations, may be disposed within thekiln wherever it may be deemed to be advantageous to place them.

In respect to the arrangement aforesaid of the ports 15 of graduatedsizes in series, l illustrate in Figure IX provision of two oppositelytapered ducts 50 and 51, each having a longitudinal slit 52 which is theequivalent of a series of ports 15 in effect of graduated sizes. Theducts 50 and 51, where employed, are reversely disposed in respect tothe taper of each, and communicate, respectively, with trunks 10 and 11.

A convertible tapering duct adapted to accommodate itself to reversal ofcirculation, is shown in Figure X, wherein is illustrated a rectangulartrunk or casing 52 having provided against one side of it a snuglyfitting juxtaposed movable cover-plate 53 connected by a pivotal support54 to the wall of the trunk 52. The plate 53 is adapted to be swung incontact with a wall of the casing 52 which is perforated by a series ofcorresponding, transversely disposed, elongated openings 55. By movementof the plate 53 on its axis 54, the series of openings 55, inconsequence of being partially covered by the said plate, may be made totaper towards one end of the duct or towards the other end thereof, atwill. Consequently, the larger end of the series of openings may beresented to- Wards the oncoming volume of circulation, to suit thedirection of flow ,of the circulating medium. The uncovered portions ofthe openings 55 in the casing 52 constitute, in effect, a graduatedseries of ports in one trunk adapted to operatively communicate with theseries of ports in the companion trunk, or

the one paired with the first named trunk, in a p manner correspondingto that already described with reference to the ports 15.

The operation of my apparatus may be, in view of the foregoingdescription, briefly described as follows.

Referring to Figure I, for example, if it be assumed that the shaft 3 isrotated in a direction to effect air delivery from the fan 1 into thetrunk 10, the effect will be to produce circulation through the trunk 11in the opposite direction. By air circulation throu h either of therespective trunks 10 and 11, etermined by the direction of circulationemployed, a static pressure therein will be built up, thereby effectingoperative communication from one set of ports 15 in one trunk with theother set of ports 15 in the other trunk. The result will be to effectwithin that portion of the interior of the kiln chamber 5, which isabove the level of the wall or walls 7 a forced movement of thecirculatory medium throu h the o enings in the stacks of stock withrying e ect on the stock.

In Figure IV, the operation is, in effect, the same, the circulation inthe trunks 10 and 11 being efiected by the operative coaction throughpressure and suction, respectively, of the fans 17 and 18.

In respect to the operation of the embodiment of my invention shown inFigure VI, the operation of the apparatus is substantially varied inonly one respect, namely, that three independent plenum chambers 29, 30,and 31, are used instead of the one plenum chamber shown in otherfigures, said plenum chambers being also reversible in operation withthe chambers 35, 36, and 3:7. Distribution of the fans by using a serlesof paired trunks in each kiln makes it possible to use large inlet andoutlet ports in proportion to the volume of air circulated than ispossible when uniform distribution of circulation is eiiected solely bycreating a high static pressure in the trunks. The static pressureagainst which the fans are made to effect circulation is considerablylessened, resulting in lower power consumption for driving the fans andthus considerable gain in circulation efliciency.

In respect to the apparatus shown in Figure VII, the operation issubstantially identlcal, in effect, with that of the apparatus shown inFigure I, for example, except that the external fan 46 shown in FigureVII is.nonreversible, and functionates in itself alone by a direct driveof air into the trunk 10 and by a return pull upon the air from thecompanion trunk 11. In other Words, the single fan 46 is contrived tokeep up continual forced circulation through ports provided in trunks asmeans of communication between aired trunks.

The functional effect of separate ports 15 trunk shown in of relativegraduated capacities is accomlished by the substitution therefor of ionitudinally disposed tapered slits 52 in t e Figure IX.

Figure XI illustrates a plurality of stock loads (two by way of exampleonly) through the horizontal interstices in which the C11- culatorymedium, with drying effect u on each load, travels in passing from oneloa to the one next adjacent in series. The effect of suchmultiplication of the number of stock loads is to increase the capacityof the kiln by merely enlarging its transverse extent, but without thenecessity of materially amplifying the capacity of the means for heatingand for driving the circulatory medium, although said capacity may be,of course, increased upon occasion if deemed to exist in any instance.

An economical advanta e in the operation of the kiln may be gained bythe employment of means for varying the speed of the fans at differentstages of the drying operations. In that regard, I have discovered that'more driving force is necessary to efiect increased rate of circulationof the drying atmosphere of the kiln when the stock loads are firstintroduced into the kiln in a wet or green state, than when afterwardsthey have given off a portion of their moisture content. The reason apears to be that the gaseous medium of circu ation, in passin throughthe interstices of the stock loads, ta es up so much of moisturetherefrom in passing through part of the load as to incapacitate it fortaking up a corresponding proportion of moisture in passing through theremainder of the load. In other words, the drying atmosphere of the kilnfunctionates to better advantage in passing through part of the distanceit has to travel inpassing through the interstices of the load than itdoes in passing through the remainder of the distance. The remedy forthat condition is to increase the rate or volume of circulation duringsuch period as the stock is wet and the condition above indicatedcontinues. This requires increase of power for such period. After thestock becomes drier, the reduction of its moisture content diminishesgradually the necessity for the higher rate of circulation, and permitsreduction of the rate of speed of circulation and of the power necessaryto efiect it. Inother words, the rate of speed of circulation is by myinvention made proportionate to the lag in the capacity of thecirculating medium to absorb moisture in passing across the surfaces ofthe drying stock loads. The term lag is, in this connection, defined tobe loss of the functionating capacity of the drying atmosphere, takinginto consideration that such capacity is diminished by loss of heat fromthe drying atmosphere as well as by increase of the moisture contentthereof. The rate of circulation desired is that which will mm der thedrying operation on the stock loads as uniform as possible, throughoutits difierent stages.

A. definite advantage of using e. greater seed of circulation at theearlier stages of it drying recess is, that it afi'ords means toovercome t e natural-draft tendency of circulation within the kiln dueto the cooling effect of evaporation oi moisture from the stockwhen themoisture content is greatest.

The use of a multi-speed fan-driving means makes it possible to effectmaterial economy in the drying of the stock loads by using a faster rateof circulation at an early stage of the drying process and a slower rateat later stages.

In other words, a greater rate of circulation at the earlier stages ofthe drying process, or at what is known in the rogressive kiln art asthe green end of the iln where the temperature at the immediate surfaceof the stock is lower and the humidity is higher, is needed to conveymore heat for evaporation purposes to the surfaces of the stock beingried. At such time there is more moisture in the stock to be evaporated,and the moisture carrying capacity of the kiln atmosphere is lower. Morecirculation is also needed at such time to remove from the surfaces ofthe stock, the moisture as soon as it is evaporated.

At a later stage of the drylng process, or-

ultimately at the dry end or: a progressive kiln when the temperature ishigher and the humidity is lower, and the transfusion rate is slower,and when there is less moisture to be evaporated and removed, themoisture-carrying capacit of the kiln atmosphere is then greater andthere is, therefore, less need at that point for a high rate ofcirculation across the stock.

Hitherto, a substantially constant rate of speed has been imparted tothe fans throughout'the whole period of the drying operation of thekiln. My invention contemplates economy in the saving of power, forinstance, through the employment of means for driving the fans atdifierent speeds or of interruptin the operation of the fans altogetherand re ying in such case upon natural draft for efiecting circulation indifierent stages of the drying operation, proportionate to thecondition, at any stage, of the drying atmosphere, as affected, forexample, by the stock to be dried. My invention in this regard, consistsin using fans of variable speed and in setting their speedproportionately to the amount of work demanded of them at diiferentstages of the drying operation.

Variable speed circulation at diiferent stages of the drying process, isbein claimed in another application Serial No. 60 ,651.

What I claim is:

1. As part of a dry kiln, a. convertible duct consisting of an oblongsubstantially rectangular trunk provided with a series of transverseelongated openings, in combination with a movable cover-plate snuglyfitting over said openin s and medially pivoted to the trunk, where ymovement of said plate may at will convert the said openings into aseries of ports graduated in size towards either end of the trunk.

2. As a part of a dry kiln, a convertible duct consisting of an oblongsubstantially rectangular trunk provided with a series of transverseelongated openings, in combination with a movable cover-plate snuglyfitting over said openings whereby movement of said plate may at willconvert the said openings into a series of ports graduated in sizetowards either end of the trunk.

3. In a dry kiln, a convertible duct consisting of a pair of laterallydisposed substantially series of openings in combination with means foroppositely tapering the openings, respectively, for air delivery andsuction so as to equally distribute the air delivery and suction at eachpair of opposite openings through the kiln.

4. In a dry kiln with lumber stacked therein, a pair of covered trunkshaving operative communication therebetween at one of their ends,respectively, means for producing cross circulation through the lumber,said means being adapt to reverse the air circulation in the trunthrough the lumber and constituting means for converting at will eitherof the trunks into a suction or an air pressure trunk, and means fordistributin the air circulation from trunk to trunk uni ormly in eachcross section of the kiln consisting of means for oppositely taperingthe louver openings on each side of the kiln at will.

5. A. dry kiln comprising a kiln chamber provided with means foraccommodation of kiln loads of stock and provided with heating means incombination with the plurality of pairs of covered trunks laterallydisposed to the stock in paired relationship, ports disposedlongitudmally of and in operative communication with said trunks,respectively, and reversible fans on longitudinal shafts for convertingone of each pair of trunks into a plenum chamber and the other into asuction chamber, whereby continuing circulation of drying circulatorymedium from one trunk to another through their ports, may be maintainedwithin the kiln from one portion of it to another through the kiln loadsof stock provided Within the kiln chamber and permeable to the saidcirculatory medium.

6. A dry kiln comprising a kiln'chamber divided within by horizontalpartition wall, and provided with means above said well foraccommodation of kiln loads of stock and provided with heating means, incombination with the plurality of trunks laterally disposed to the stockin paired relationship below said wall, ports in said wall disposedparallel trunks provided with a i of and longitudinally of and inoperative lateral communication with said trunks, respectively, andreversibly operative fans on a longitudinalshaft for converting one ofeach pair 5 of said trunks into a plenum chamber and the complementarytrunk into a suction chamber whereby continuin circulation of the dryingcirculatory me ium from one trunk to another may e maintained within thekiln from one portion of it to another throu h kiln loads of stockprovided within the kiln chamber above the horizontal partition wall andpermeable to the said circulatory medium.

7. A dry kiln comprising a kiln chamber divided within b horizontalpartition wall and provided wit means above said wall for accommodationof kiln loads of stock and provided with heating means in. combinationwith a plurality of paired trunks laterally dispose to the stock inPaired relationship below said wall, ports 0 graduated ca acities insaid well disposed longitudinal y of and in operative lateralcommunication wit said trunks, respectively, and mechanical meansconsisting of reversible fans on one shaft for converting one of eachpair of said trunks into a plenum cham r and the complementary trunkinto a suction chamber, whereby continuing circulation of dryingcirculatory medium irom one trunk to another may be maintained withinthe kiln from one portion oi it to another through kiln loads of stockprovided within the kiln chamber above the horizontal partition wall andpermeable to the said circulatory medium.

8. A dry kiln comprising a kiln chamber divided within by horizontalpartition wall, and provided wit means above said wall for accommodationof kiln loads of stock and provided with heating means in combinationwith a plurality of trunks laterally disposed to the stock in pairedrelationship below said well, ports in said wall disposed longitudinalinoperative lateral communication d trunks, respectively, and a multitrotatin on a common member we communication with one of said convertingsaid trunks on one side of the stock iced into a plenum chamber andthereon the side into a suction chamber, whereby continuing circulationof drying circulatory medium from one trunk to another through theirports may be maintained within the kiln from one portion of it toanother through 'iln loads of stock provided within the kiln chamberabove the horizontal partition wall and permeable to the saidcirculatory medium.

9. A dry lriin comprising a kiln chamber divided within by horizontalpartition for support of kiln loads of drying stock in combination withpaired trunks laterally disposed to the stock disposed below saidpartition and separated by vertical wall supporting said partition, saidwall being shorter than the lengthof the kiln chamber so as to renderthe trunks intercommunicating below the horizontal partition, ports insaid partition for rendering the trunks intercommunieating above saidpartition, means for heating said trunks, respectively, and reversiblefan mechanism on one longitudinal shaft in operative communication withthe trunks.

1t). A dry kiln comprising a kiln chamber dlvided within by horizontalpartition, in combination with disposed independent intercommunicating aseries of laterally paired trunks in end to end assemblage below saidpartitions each having and fan mechanism on longitudinal shafts. inoperative communication therewith below said partition and portscommunicating through said partition with the respective trunks forafiordin means of intercommunieating within the kiln chamber betweeneach pair of trunks above said partition.

in testimony whereof, I have hereunto set my hand.

J. FORREST COBB.

heating means,

' ion

